Rolling mill and method of operating the same



L. IVERSEN April 5, 1938.

ROLLING MILL AND METHOD OF OPERATING THE SAME 4 Sheeis-Sheet l Filed June 14, 1935 INVENTOR Lama-1M April 5, 1938. NERSEN 2,113,050

ROLLING MILL AND METHOD OF OPERATING THE SAME Filed June 14, 1955 4 Sheets-Sheet 2 f g 3 E J3 L. IVERSEN April 5, 1938.

ROLLING MILL AND METHOD OF OPERATING THE SAME Filed June 14, 1955 4 Sheets-Sheet 3 Aplll 5, 1938. IVERSEN ROLLING MILL AND METHOD OF OPERATING THE SAME 4 Sheets-Sheet 4 Filed June 14, 1955 INVENTOR Patented Apr. 5, 1938- ROLLING MILL AND METHOD OF OPERAT- ING THE SAME" Lorenz Iversen, Pittsburgh, Pa., assignor to Mesta Machine Company, Pittsburgh, 2a., a corporation 01' Pennsylvania Application June 14, 1935, Serial No. 26,588 3 Claims. (01. 80-38 This invention relates to rolling mills and the operation thereof and is herein particularly de-' scribed as applied to a mill of the 4-high type for strip rolling. The rolling of strip, especially if it 5 has a high ratio of width to thickness, entails the use of very high roll pressures and consequently the roll neck bearings are subject to extremely high unit loads. This fact has militated against the use of bearings of the lubricated journal type, and roller bearings have been employed to a considerable extent. There are numerous advantages in bearings of the lubricated journal type but they are open to the objection that when the mill is standing idle the pressure of the roll neck against the journal bearing squeezes out most of the film of lubricant. While it takes only a relatively short time to re-establish the film after the mill has started up, the wear attendant upon starting and re-establishing the film may be considerable, under extreme conditions the nondriven rolls may even refuse to turn, and variations in the thickness of the film may adversely affect the gauge of the product. The difficulty is particularly marked on the bottom roll of the mill because theweight of the roll is exerted downwardly and tends constantly to break the film of lubricant. The difiiculty is not met in the bearings of the top roll because the top roll is thrust upwardly while it is working and, of course, it tends of its own weight to drop away from the upper part of the bearing 'shell and is restrained only by the lower part of the shell. In consequence there is no tendency to break the film at the point where it is most required for the top roll. Where mills of the backed-up type are used, the bearings of the bottom roll must carry the dead weight of the backing roll or rolls as well as the weight of the bottom work roll.

It is well recognizedihat a bearing of the lubricated journal type is subject to practically no wear so long as the oil film is maintained; but

the problems peculiar to rolling mill practice have limited the applicability of bearings of this type. The present invention, by doing away with the principal cause for breakdown of the oil film, vastly enlarges the field of applicability of such bearings. I eliminate the tendency toward breaking down of the oil film due to weight of .the rolls by balancing out the eight of the roll in large measure and particularly of the bottom roll. Roll balancing means, broadly speaking, are well known, but such roll balancing devices do not function to lessen the unit pressure on the bearings and minimize the tendency toward squeezing out or breaking down the ,oil film.

In the accompanying drawings illustrating certain preferred embodiments of the invention,

Figure 1 is a side elevation partly broken away showing a mill of the 4-high type having my invention applied thereto;

Figure 2 is a horizontal section to enlarged scale through the mill of Figure 1 taken ,on a plane tangent to the bottom of the bottom backing roll;

Figure 3 is a transverse vertical section showing the roll balancing mechanism in more detail;

Figure 4 is a section on the line IVIV of Fig ure 3;

Figure 5 is a view corresponding to Figure 3 but showing a modified form of construction;

Figure 6 is a'view corresponding to a portion of Figure 5 but to enlarged scale and partly broken away;

Figure '7 is a section on the line VIIVII of Figure 5;

Figure 8 is a view corresponding to Figure 3 but showing a still further modification; and

Figure 9 is a section on the line IXIX of Figure 8.

The mill illustrated in Figures 1 to 4 inclusive comprises housings 2 having windows 3 therein in which are mounted backing rolls 4 and 5 with intermediate work rolls 6 and 'l. The backing rolls have necks working in chocks 8, the bearings being of the lubricated journal type. Suitable oil connections are indicated at 9. A highly satisfactory form which the bearing may take is more specifically described and claimed in my copending application Serial No. 727,701, filed May 26, 1934. The necks of the working rolls 6 :1 and l are carried in chocks Ill.

8. In a modern mill this weight may be as much as 125,000 pounds. Such a load tends to squeeze the oil out of the bearings so that the oil film is ruptured or else will rupture immediately onstarting up and before the rolls have rotated sufiiciently to entrain a fresh supply of oil, carry it into the journal, and re-establish or renew the film. In order to reduce the load on the bearings of the lower roll, the roll is engaged externally of the journal surfaces and urged upwardly.

In this form-of the invention the balancing is accomplished by means of a thrust roller l2 running on bearings l3 mounted on a spindle I4.

The thrust roller I 2 bears against the working face of the bottom roll 4 and extends over a substantial portion of its width. The surface of the roll 12 is highly finished and does not mar the hardened surface of the backing roll. It runs freely on its bearings so that there is no tendency to scratch even if any foreign particles should accidentally be entrained on the roll surfaces. Provision is made at I5 for lubricating the bearings l3. The spindle I4 is carried in a slide 38 which is movable vertically in a casing ll supported between the housings 2. The casing l'l contains nested coil springs 3 which exert an upward force against the roll 4. This force is not sufficient to lift the weight of the bottom roll out of its bearings but is sufficient to reduce in great measure the pressure exerted on the oil film in the bottom journal bearings.

The springs act against the slide l6 through collars l9 and the collars slide on studs having bottom flanges 2| which lie below the bottom ends of the springs. Heads 22 on the studs limit the expansion of the springs l8. This permits' of initially compressing the springs l8 so that they are contained in a relatively small compass. The length to which the springs can expand is correspondingly limited and therefore the amount of upward movement of the rolls I2 is limited. It is not intended that this limit of movement shall be reached so long as the mill rolls are in place, but when it becomes necessary to change the mill rolls it is important that there be some such limit on the amount of upward movement of the roller 12.

Figures 5 to 7 illustrate a modified form of construction in which the roll I20. is carried in bearings on a spindle Ma, the spindle being urged upwardly by hydraulic plungers working in cylinders 3|. The cylinders 3| are formed in a casing Ila lying between the housings 2a and are connected through passages 32 to a conduit 33 which is connected to a controlled supply of fluid pressure. With this form of apparatus, the upward movement of the roller l2a is limited when a roll change is to be made by merely cutting off the fluid pressure.

Figures 8 and 9 show still another modification wherein the pressure roller l2b is mounted on a spindle Mb which, in turn, is carried by slides lll movable up and down in a casing l'lb supported between the housings 2b. The bottom of each slide 40 is engaged by one arm M of a lever pivoted at 42. The longer arms 43 of such levers are connected through links M- to a counter-weight 45. The levers constitute a multiplying system whereby with a weight of reasonable size a considerable upward force can be exerted. In this case theupward movement of the roller l2b is limited by the engagement of faces 46 on the arms 4| of the levers with cooperating faces 41 on the housing l'lb.

It is often necessary to redress the surfaces of the mill rolls and during the life of a roll there is a corresponding reduction in weight, which weight reduction is often considerable in amount.

Preferably the upward force exerted by the balancing means is slightly less than the minimum weight of the roll, with due regard to dressing down of the roll body.

Where I have referred herein to bearings of the journal type or of the lubricated journal type, I have intended to refer to those bearings wherein the shaft has sliding as distinguished from rolling friction with its supprting surface, and I mean to include not only babbitt lined bearings but bearings of other material and construction, as, for example, water-lubricated bearings made of composition material.

While I haveillustrated and described certain preferred embodiments of my invention, it is to be understood that the same is not limited thereto but may be otherwise embodied and practiced within the scope of the following claims.

I claim: I

1. In the method of operating a rolling mill having rolls including a bottom roll with roll neck bearings of the lubricated journal type, the steps consisting in intermittently rotating the rolls and rolling material in the mill, resisting the rolling force transmitted through the bottom roll by means of the neck bearings, and, at least during those times when the bottom roll it not rotating, yieldingly applying to the body of the roll an upward force limited in amount to less than the dead weight of the bottom roll but equal to a substantial part of said weight, thereby substantially lessening the unit pressure in the bearings and limiting the extrusion of lubricant under such dead load, thus to insure the presence of a lubricant film in the bearings adequate to supportthe rolling load on resumption of rolling in the mill.

2. In the method of operating a rolling mill having rolls including a bottom roll with roll neck bearings of the lubricated journal type, the steps consisting in intermittently rotating the rolls and rolling material in the mill, resisting the rolling force transmitted through the bottom roll by means of the neck bearings, and, at least during those times when the bottom roll is not rotating, yieldingly applying to the body of the roll an upward force limited in amount to less than the dead weight of the bottom roll and the parts supported thereby but equal to a substantial part of said weight, thereby substantially lessening the unit pressure in the bearings and limiting the extrusion of lubricant under such dead load, thus to insurethe presence of a lubricant film in the bearings adequate to support the rolling load on resumption of rolling in the mill.

3. In the method of operating a rolling mill having rolls including a bottom roll with roll neck bearings of the lubricated journal type, the steps consisting in intermittently rotating the rolls and rolling material in the mill, resisting the rolling force transmitted through the bottom roll by means of the neck bearings, engaging the body of the roll with a pressure roller and yieldingly applying to the body of the roll through said pressure roller an upward force limited in amount to less than the dead weight of the bottom roll but equal to a substantial part of said Weight, thereby substantially lessening the unit pressure in the bearings and limiting the extrusion of lubricant under such dead load, thus to insure at all times the presence of a Inbricant film in the bearings adequate to support the rolling load.

LORENZ IVERSEN. 

